The present invention relates to remote irradiation systems and, more particularly, to a system and method for irradiating a target with light from a high-intensity source, at a power density almost as high as that of the light emitted by the source.
Conventional metal-halide, xenon, argon, halogen, microwave-sulfur and related lamps possess radiating sources (e.g., filaments, discharge arcs or radiating spheres) of high power density at the source surface. Such flux levels are well suited to applications that range from high-temperature heating (such as semiconductor processing), to certain medical procedures (such as tissue welding, coagulation, external skin disorder treatment, cosmetic surgery, and others), to remote lighting.
There is no fundamental principle that forbids restoring these high power densities on distant targets; yet the inherently high flux levels have not been successfully harvested, for a number of related reasons. First, the surface area over which radiation is emitted is small relative to lamp size and is deeply recessed within a transparent envelope. Therefore the power density at the entrance to any light-collection device is reduced substantially. Second, imaging systems tend to suffer large aberrations, in particular for collecting rays from the large angular emission range of these sources. Hence either their collection efficiency is low, or their average power density is compromised significantly. If the imaging system has high collection efficiency, then it tends to be complex and unwieldy.
The optical performance of a single rotationally-symmetric device is inherently limited by the geometric (shape) mismatch between source and target due to skewness conservation. This translates into either substantial ray rejection for high flux density, or markedly diluted power density at high collection efficiency.
There is thus a widely recognized need for, and it would be highly advantageous to have, a system and method for efficiently concentrating the collected radiation, from its diluted power density outside the transparent envelope that encloses the light source, back to the flux level intrinsic to the source.
According to the present invention there is provided a system for delivery of high intensity light to a target, including: (a) a source of the high intensity light; and (b) a plurality of nonimaging concentrators surrounding at least a portion of the source, each of the nonimaging concentrators having an entrance aperture, all of the entrance apertures facing the source.
According to the present invention there is provided a method for delivering high intensity light to a target, including the steps of: (a) providing a source of the light; (b) concentrating at least a portion of the light emerging from the source, using at least one nonimaging concentrator; and (c) conducting at least a portion of the concentrated light to the target.
According to the present invention there is provided a system for delivery of high intensity light to a target, including: (a) a source of the high intensity light; and (b) a mechanism, surrounding substantially all of the source, for collecting the light and conducting the light to the target.
According to the present invention there is provided a method for delivering high intensity light to a target, including the steps of: (a) providing a source of the light; (b) surrounding substantially all of the source with a mechanism for collecting the light; (c) collecting the light, using the mechanism; and (d) conducting the collected light to the target.
According to the present invention there is provided a method for efficiently delivering light from a source along an optical path to a target, including the step of including a nonabsorbing monochromator in the optical path.
The principle of the present invention can be best understood by reference to the embodiment thereof illustrated schematically in FIG. 1. A spherical transparent envelope 12, concentric with and surrounding a radiating source 10, is tiled with small light channels 14 of circular cross section. Light channels 14 may be optical fibers or light pipes. Losses due to the imperfect packing of a spherical surface with small circular apertures are on the order of about 10%. Distal ends 16 of light channels 14 are grouped to form a narrow angle input to a maximum-flux nonimaging concentrators 18, one of which is shown in FIG. 1. The total area of absorbers 20 of concentrators 18 is equal to the surface area of source 10, so the absorber power density approaches the power density of source 10. In addition to the loss associated with imperfect tiling of the spherical surface of envelope 12 at the light collection side, there is 10% or more dilution of power density at distal ends 16 in packing light channels 14 into entrance apertures 22 of concentrators 18. In principle, the packing losses can be eliminated by fusing distal ends 16.
The drawback of this embodiment is that an enormous number of channels 14 are required. Preferably, then, a small number of maximum-flux nonimaging concentrators that are tailored to the source are placed with their entrance apertures as close to the lamp envelope as possible, substantially surrounding the lamp. The absorbers of these concentrators are optically coupled to a far smaller number of light channels than in the design of FIG. 1, and these light channels are used to transport radiation to remote locations.
The high intensity light of the present invention includes any suitable form of electromagnetic radiation that obeys the laws of geometric optics on the relevant length scale, particularly visible light, infrared light and ultraviolet light. Although the scope of the present invention includes designs in which the concentrators are in contact with the source, for example if the source is a fluorescent lamp, the emphasis herein is on embodiments with sources embedded within transparent envelopes, with the concentrators in contact with the envelopes. These sources include conventional high-intensity lamps such as metal-halide lamps, noble gas (for example, argon or xenon) lamps, halogen lamps and microwave-sulfur lamps.
There are two classes of common high-intensity lamps:
(1) lamps with elongated sources, with the length of the cylindrical filament or discharge region being far greater than the source diameter; and
(2) lamps with compact sources, e.g., spherical radiators or short squat arc discharges, having dimensions far smaller than the envelope dimensions.
In the case of a lamp with an elongated source and a similarly elongated envelope, the concentrators are similarly elongated. Typically, both the lamp and the concentrators are straight, with the concentrators disposed parallel to the lamp. The scope of the present invention includes other geometries, however, for example concentrators wrapped helically around a straight lamp. In the case of a lamp with a substantially spherical envelope, the concentrators are disposed around the envelope according to the surfaces of a Platonic solid, most preferably a dodecahedron.
The scope of the present invention includes concentrators based on interior reflective surfaces only, concentrators consisting of dielectrics, and concentrators that are lens-mirror combinations, with the latter two types of concentrators being preferred. The shapes of the concentrators are designed in accordance with the edge-ray principle of nonimaging optics, as described below.